Multiple-satellite sensors algorithm wake up and reset strategy for an inflatable restraint system

ABSTRACT

An air bag system ( 12 ) provides a central controller ( 14 ), a multiple of satellite sensors ( 16 ) and a multiple of deployable air bags ( 18 ). The central controller ( 14 ) runs the impact event algorithms. The number of satellites which are allowed to activate algorithms at any one time is limited. The minimum number of satellites required for full protection is the maximum number of satellite sensors allowed to wake up an impact event algorithm at any one time. An order for algorithm wake is also specified since the number of algorithms allowed is less than the total number of satellite sensors.

The present application claims priority to U.S. Provisional PatentApplication Ser. No. 60/389,583, filed 18 Jun. 2002.

BACKGROUND OF THE INVENTION

The present invention relates to an inflatable restraint system, andmore particularly to an algorithm which limits the number of satellitesensors which may be active at one time.

Driver side or passenger side supplemental inflatable restraint (SIR)systems typically include an air bag stored in a housing module withinthe interior of the vehicle in close proximity to the driver and one ormore passengers. SIR systems are designed to actuate upon suddendeceleration so as to rapidly deploy an air bag to restrain the movementof the occupants.

More recently, SIR systems are being extended to protect occupants inall rows of the vehicle. Protection of these occupants is accomplishedby equipping the vehicle with multiple rows of side impact eventsatellite sensors which have the ability to provide data and lead thedeployment of airbags or other passive safety restraints.

The side impact event satellite sensors may either be a “decision maker”or a “data sender”. “Decision maker” satellites are more expensivebecause they require a microprocessor to run an algorithm. “Datasending” satellites are preferred from a cost perspective because theydo not require a microprocessor. The data sending satellites communicateraw data to a central controller, which contains a microprocessor forexecuting the algorithm.

The central controller is responsible for running all the necessaryimpact event algorithms. This may include algorithms for front/rearimpact events, algorithms for rollover events, and algorithms for sideimpact events. The controller must have enough throughput to execute allof these algorithms while still providing normal diagnostic functions.Therefore, the required runtime for each algorithm must be kept as lowas possible.

Each row of side impact event protection usually requires two impactevent satellite sensors in order to deliver a desired level ofperformance. One satellite is for the driver side and one is for thepassenger side. Each satellite has the ability to wake up an algorithmin the central controller. Therefore, a car with two rows of sideprotection would have four satellites that may try to run four sidealgorithms simultaneously.

Disadvantageously, running numerous algorithms could lead tomicroprocessor runtime issues. The task may be further complicated dueto the aggressive deploy times required for side impact events.

Accordingly, it is desirable to provide a wake up and reset strategy,which minimizes the runtime required by the satellite sensor algorithms.

SUMMARY OF THE INVENTION

The air bag system according to the present invention provides a centralcontroller, a multiple of satellite sensors and a multiple of deployableair bags. The satellite sensors transmit data to the central controllerwhich runs side algorithms to sense side impact events.

The central controller runs the necessary impact event algorithms.Therefore, the required runtime for each algorithm must be kept as lowas possible as running numerous algorithms may lead to microprocessorruntime issues. The present invention minimizes runtime by limiting thenumber of satellites which are allowed to activate algorithms at any onetime. The minimum number of satellites required for full protection isthe maximum number of satellite sensors allowed to wake up an impactevent algorithm at any one time. An order for checking satellite sensorwake up is also specified since the number of algorithms allowed is lessthan the total number of satellite sensors.

The present invention therefore provides a wake up and reset strategy,which minimizes the runtime required by the satellite sensor algorithms.

BRIEF DESCRIPTION OF THE DRAWINGS

The various features and advantages of this invention will becomeapparent to those skilled in the art from the following detaileddescription of the currently preferred embodiment. The drawings thataccompany the detailed description can be briefly described as follows:

FIG. 1 is a schematic view of an exemplary vehicle embodiment for usewith the present invention;

FIG. 2 is a chart comparing satellites which may be active according tothe present invention;

FIG. 3 provides pseudo code for an algorithm wake up strategy accordingto the present invention;

FIG. 4 illustrates status bytes for an “algorithm_entry_enable” byte andan “algorithm_active_status” relative to an occupant location;

FIG. 5 provides pseudo code for an algorithm-reset strategy according tothe present invention; and

FIG. 6 is a graphical representation of an impact event.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

FIG. 1 illustrates a general schematic view of a vehicle 10 having anair bag system 12. The air bag system 12 generally includes a centralcontroller 14, a multiple of remote satellite sensors 16 and a multipleof deployable air bags 18. Preferably, one or more air bags 18 arelocated to the side of a vehicle seat 20.

The satellite sensor 16 communicates with the controller 14 to sense adeploy event such as a side impact. In response to signals from thesatellites sensor 16 the controller 14 determines whether to deploy theair bag 18 through logic stored in the controller 14. The satellitesensors 16 are preferably located in the side 22 of the vehicle 10adjacent the related air bag 18. It should be understood that other airbag arrangements and sensor locations will likewise benefit from thepresent invention.

The satellite sensors 16 may be based on several different sensingprinciples such as acceleration and pressure. The satellite sensors 16may also either be a “decision maker” or a “data sender”. “Decisionmaker” satellite sensors may be more expensive because they require aself-contained microprocessor to run an algorithm. “Data sending”satellites are preferred from a cost perspective because they do notrequire a microprocessor as they simply communicate raw data to thecentral controller 14, which contains a microprocessor for executing analgorithm for each satellite sensor.

The central controller 14 is responsible for running all the necessaryimpact event algorithms for each of the satellite sensors 16. This mayinclude algorithms for front/rear impact events, algorithms for rolloverevents, and algorithms for side impact events. The controller 14 musthave enough throughput to execute all of these algorithms simultaneouslyand still carry out normal diagnostic functions. Therefore, the requiredruntime for each algorithm is preferably maintained as low as possible.

Each row of seating which is to have side impact protection utilizes twosatellite sensors 16 in order to deliver a desired level of performance.One satellite 16 is for the driver side and one is for the passengerside for each row or seating. Each satellite operates to wake up animpact event algorithm in the central controller 14 as generally known.Therefore, a vehicle 10 with two rows of seating has four satellitesensors 16 and the central controller 14 may attempt to run fouralgorithms if simultaneously communicated with by each satellite sensor16.

Running numerous algorithms may lead to microprocessor runtime issues.The present invention minimizes runtime through limiting the number ofsatellite sensors which are allowed to activate algorithms at any onetime. As it is preferred to maintain full protection for both sides ofthe vehicle in case an impact occurs simultaneously on both sides, theminimum number of satellites required, which may enter an impact eventalgorithm at any one time while still providing for full vehicleprotection is limited as follows:Minimum number of satellites=(Total number of satellites/2)+1

The “+1” allows a satellite sensor 16 on an opposite side of an impactevent to wake up if the opposite side is also struck. To reduce runtime,the minimum number of satellites required for full protection is themaximum number of satellite sensors 16 allowed to wake up an impactevent algorithm at any one time. FIG. 2 summarizes the maximum number ofsatellites allowed to be active in an algorithm at the same time for upto four rows of seating.

Referring to FIG. 3, pseudo code for the algorithm wake up strategy fora driver-side front row satellite 16 is provided. The pseudo coderepresents the logic within the central controller 14 for operation ofthe air bag 18 in response to signals from the satellite sensor 16.Implementation of the present invention preferably utilizes an algorithmwake up criterion, an algorithm reset criterion, and an active algorithmcounter. Other status flags may also be utilized.

The algorithm wake up criterion is selected such that a satellite sensor16 wakes up the impact event algorithm within the central controller 14only if its impact event signal exceeds a pre-defined limit in theimpact event direction. This minimizes unstruck satellites from enteringthe impact event algorithm before struck satellites. One preferredsignal is velocity with offset of the satellite sensor. It should beunderstood that additional or alternative signals may also be utilized.Any signal that is used for the purpose of impact event algorithm wakeup, however, must be calculated at all times.

The order of checking for impact event algorithm wake up is alsoimportant since the number of impact event algorithms allowed is lessthan the total number of satellite sensors 16 because it may be possiblethat all satellite sensors 16 may meet their wake up criteria at thesame loop. Preferably, the front row driver position is checked first,followed by the front row passenger. Next, the second row driver andthen the second row passenger are checked, and so on. Priority is givento the front rows because they are more likely to have occupants.

When a satellite sensor wakes up an impact event algorithm, a counter 24(FIG. 1) is preferably incremented to keep track of the number of activesatellite sensors 16. If the maximum number of active satellite sensors16 (FIG. 2) is reached, then no further side algorithms are allowed toinitiate. When a satellite sensor's algorithm resets the counterdecrements.

Satellite sensors 16 are preferably prevented from entering the impactevent algorithm in the middle of an impact event because this may leadto unpredictable behavior. Therefore, satellite sensors 16 arepreferably prevented from starting an impact event algorithm unlessknown to be “quiet” just before the attempt to wake up. This ispreferably achieved by maintaining two status bytes, which contain onebit for each satellite sensor 16. One status byte, which may be called“algorithm_active_status”, indicates whether a satellite sensor's 16algorithm is currently active. A bit value of ‘1’ or TRUE indicates thatthe corresponding satellite sensor's algorithm is currently active. Theother status byte, which may be called “algorithm_entry_enable”,indicates which satellites are allowed to enter the algorithm. This bitis set to ‘1’ or TRUE if this satellite is allowed to start analgorithm. This bit is cleared to prevent this satellite from startingan algorithm.

Referring to FIG. 4, the status bytes have the same format and arepreferably set up such that the left nibble (most significant) will beassigned to the driver side satellites. The right nibble (leastsignificant) is assigned to the passenger side satellite sensors 16.

During normal operation, i.e., no impact event, the“algorithm_entry_enable” byte contains all ones and the“algorithm_active_status” byte contains all zeros. No side algorithmsare currently active and all satellite sensors 16 may start analgorithm. During a impact event, any satellite sensor 16 may enter orexit its algorithm as long as the maximum number of allowable activesatellites has not been reached (FIG. 2).

As the first satellite sensor 16 wakes up, its respective bit in the“algorithm_active_status” byte gets set to ‘1’, the“algorithm_entry_enable” byte remains unchanged, and the activesatellite counter 24 (FIG. 1) is incremented. When the maximum number ofallowable satellites are simultaneously active in their algorithms, the“algorithm_entry_enable” status byte is masked (logical AND) by the“algorithm_active_status” byte. The satellite sensors 16, which are notcurrently in the algorithm, have their bits cleared and are therebyprevented from entering for the remainder of the impact event.

When a satellite sensor's algorithm ends, its bit in the“algorithm_active_status” byte is cleared and the active satellitecounter decrements. The “algorithm_entry_enable” byte is reset to allones after the last satellite sensor resets out of its algorithm,thereby indicating that the impact event has ended. For example only, ina vehicle with six side impact event satellites, only the first foursatellites that start and remain in an algorithm would be allowed to beactive in the algorithm for the entire impact event. These first foursatellites have the ability to reset and reenter their respectivealgorithms during a single impact event. The fifth and sixth satellitesare prevented from entering their algorithms until the current impactevent has expired.

Referring to FIG. 5, pseudo code for an algorithm-reset strategy for thedriver-side front row satellite is provided. The satellite sensorsshould reset out of their algorithm when their impact event signals havequieted down. Preferably, identification of a low signal for a givenperiod of time is utilized therefor, however, several methods mayalternatively or additionally be provided. This signal is preferably anacceleration, a velocity with offset, or an averaged acceleration.

Referring to FIG. 6, a representative impact event is illustrated. Twovehicles V1 and V2 are approaching an icy intersection, V1 going northand V2 going west. At the intersection V2 strikes V1 perpendicularly(“T-bone”) and pushes it into a tree T off the side of the road. If V1has two rows of side protection (i.e. four side impact event satellitesensors) and only three out of the four satellites may execute analgorithm at any one time, the following time line may happen.

At time 1 (Pre-impact event), V1 is driving under normal conditions. Allsatellite sensors are quiet (i.e. no side algorithms are active) andtherefore all satellite sensors are enabled to wake up.

At time 2, V1 is struck on the right side by the V2. This causes bothfront row and second row satellites on the right side to activate theiralgorithms. Therefore, only one more satellite sensor 16 on the oppositeside is allowed to enter its algorithm. This impact is not severe enoughto require a side airbag deployment command.

At time 3, V1 and V2 slide together along the icy road in the northwestdirection. During this time, both right side satellite sensors 16 becomequiet and eventually reset. After reset, the entire vehicle is quiet andtherefore all satellite sensors are enabled to activate.

At time 4, V1 is pushed into the tree T near the front row, left sidesatellite sensor, which wakes up its impact event algorithm. The impactevent forces propagate quickly to the second row, left side satellitesensor, which also wakes up. The sudden stop against the tree T causesadditional forces to occur on the right side where the two vehicles arejoined together. These forces are large enough to activate bothsatellite sensors on the right side, however, only three satellitesensors may be active at any one time (FIG. 2). Therefore, the front rowpassenger side is checked first for algorithm activation due topriority. This front row passenger side satellite sensor does wake upits algorithm and becomes the third and final active satellite for thisevent.

The second row, passenger side satellite is disabled until the entirevehicle is quiet (i.e., no side algorithms are active).

The foregoing description is exemplary rather than defined by thelimitations within. Many modifications and variations of the presentinvention are possible in light of the above teachings. The preferredembodiments of this invention have been disclosed, however, one ofordinary skill in the art would recognize that certain modificationswould come within the scope of this invention. It is, therefore, to beunderstood that within the scope of the appended claims, the inventionmay be practiced otherwise than as specifically described. For thatreason the following claims should be studied to determine the truescope and content of this invention.

1. A method of limiting the run time of an airbag system comprising thesteps of: (a) limiting a total number of satellite sensors which enteran impact event algorithm of a central controller during an impact eventto: (total number of satellite sensors/2)+1.
 2. A method as recited inclaim 1, further comprises the step of: (b) tracking each satellitesensor entry and exit from the impact event algorithm.
 3. A method asrecited in claim 1, further comprises the step of: (b) tracking wheneach satellite sensor is active within the impact event algorithm. 4.(canceled)
 5. A method as recited in claim 1, further comprises the stepof: (b) maintaining two status bytes for each satellite sensor.
 6. Amethod as recited in claim 1, further comprises the steps of: (b)checking a front row driver position for impact event algorithm wakeup;and (c) checking a front row passenger position for impact eventalgorithm wakeup after said step (b).
 7. (canceled)
 8. A method oflimiting the run time of an airbag system comprising the steps of: (a)checking a front row driver position satellite sensor for impact eventalgorithm wakeup; (b) checking a front row passenger position satellitesensor for impact event algorithm wakeup after said step (a); and (c)limiting a total number of satellite sensors which enter an impact eventalgorithm of a central controller during an impact event to: (totalnumber of satellite sensors/2)+1.
 9. A method as recited in claim 8,further comprises the step of: (d) maintaining two status bytes for eachsatellite sensor.
 10. A method as recited in claim 9, further comprisesthe step of: (e) tracking each satellite sensor entry and exit from theimpact event algorithm with one of the two status bytes.
 11. A method asrecited in claim 9, further comprises the step of: (e) tracking wheneach satellite sensor is active within the impact event algorithm withone of the two status bytes.
 12. A method as recited in claim 1, furthercomprises the step of: (b) permitting wake up of only one satellitesensor on a vehicle side opposite an impact event.
 13. A method asrecited in claim 5, further comprises the step of: (c) maintaining analgorithm_active_status byte defining whether the satellite sensor iscurrently active; and (d) maintaining an algorithm_entry_enable bytedefining whether the satellite sensor is available to enter the impactalgorithm.
 14. A method as recited in claim 8, further comprises thestep of: (d) permitting wake up of only one satellite sensor on avehicle side opposite an impact event.
 15. A method as recited in claim9, further comprises the step of: (e) maintaining analgorithm_active_status byte defining whether the satellite sensor iscurrently active; and (f) maintaining an algorithm_entry_enable bytedefining whether the satellite sensor is available to enter the impactalgorithm.